Method of treating cresylic pitch to obtain tar-acids therefrom



April c. F. wlNANs Patented Apr. 16, 1946" METHOD OF TREATIN G CRESYLICPITCH TO OBTAIN TAR-ACIDS THEREFROM .Charles F. Winans, Borough ofBeaver, Beaver o County, Pa., assigner, by mesne assignments, to KoppersCompany, Inc., a corporation of `Delaware Application December 18, 1942,Serial No. 469,446

. 3 Claims; )(Cl. 260--627) This invention relates to the treatment of apitchy carbonaceous material, formed in tar acid recovery processes, toobtain valuable products from such material.V

The particular material treated by the process of the present inventionis known as cresylic pitc It is formed as a pitchy residue inthedistillation of tar acids obtained from coal tar or n other tar acidbearing oils. These oils containing tar acids are initially treated in awell-known manner with caustic 'alkali to form tar acid salts which areseparated from the unreacted, undissolved oil. The `separated tar acidsalts are sprungby means ofcarbon dioxide or the equivalent, to formfree tar acids. The recovered free tar acids are subjected to fractionaldistillation to obtain such tar acids as phenol, cresols, and xylenols.i .i

The cresylic pitch obtained as a residue in the distillation of therecovered tar acids is a very viscous, black, tarry material ofcharacteristic odor, and is highly complex in its chemical composition.It is difficult to handle, and, in general, it is considered a distressproduct, little speciiic use having heretofore been found for it, andaccumulations thereof being somewhat of a plant nuisance.

A cresylic pitch sample was found by analysis Ito contain approximately10.15% water,^9.23% ash (8.15% sodium carbonate, 0.93% iron oxide,

and 0.15% other inorganic oxides such as those of aluminum and silicon)and 80.72% organic matter. Mere distillation of cresylic pitch by itselfunder vacuum yieldsonly small amounts of distillate and mainly a residueofcoke. In fact it is impossible to distill the pitch without excessivecoking and consequent decomposition.

An object of the present invention isto provide processes for convertingcresylic Pitch into more readily distillable fractions yielding variousvaluable compounds, including particularly tar acids, and alsovarioususeful hydrocarbons. A further object is to provide a method oftreating cresylic pitch under conditions favorable for the generation oftar acids from such pitch. Another object is to provide a process `forcyclically treating cresylic pitch whereby relatively high yields ofcommercially useful products are obtained.

The invention comprises, broadly, hydrogenating cresylic pitch with or.without catalyst preferably at raised temperatures and preferably atsuperatmospheric pressures. Before hydrogenation, the cresylic pitchmay, if desired, be treated with a mineral acid, by which treatment sometar acids are rendered available. The acid treatment in itself may beemployed as a means of providing appreciable yields of tar acids. `The Yacid treatment followed byhydrogenation, however, is a more highlyelfective method of beneciating the cresylic pitch. l

' If the cresylic pitch as received from atar acid plant is to besubjected to a preliminary acid treatment before hydrogenation, it ismixed with an excess of dilute mineral acid such as sulphuric orhydrochloric acids, thereby completely destroying the alkalinity ofthecresylic pitch. The

resulting mixture is washed with hot onwarm water to remove the excessacid, or to render the pitch neutral, and also to .remove solubleinorganic salts. The wet material is heated under reduced pressure toremove Water, whereaiter the material is heated in a still to about1505A C. at about 1.5 mm. to removetar acids. A yield of agout 20% to30% tar `acids is thereby obtaina e.

The pretreated cresylic pitch, from which `inorganic material andacid-converted products are removed, is in excellent condition forhydrogenation. Either this pretreated pitch or the raw .cresylic pitchis subjected to the hydrogenation treatment described hereinbelow.

When the pitch is subjected to the action of hydrogen or of ahydrogenating `gas undersutable conditions, a liquefaction of the pitchoccurs, thereby furnishing a mobile liquid from which a major portion isdistillable up to about 275 C. at atmospheric pressure. The' distillatecontains up to, or about tar acids comprising phenol (CsHsOH) cresols,xylenols, and some higher phenolic bodies. The non-phenolic portion ofthe distillate comprises benzene, toluene, xylene,

'cyclohexana cyclohexanol, solvent naphtha,

naphthalene, and other neutral oil constituents. Fractions of thedistillate boilingin a range of 200 to 250 C. also contain smallproportions of tar bases such as quinoline, quinaldine,isoquin oline andothers which may be separated from the said distillate. The residue leftafter distilling desired fractions fromfthe beneciated pitch may befurther hydrogenated to furnish additional amounts of valuable products.

The temperature and pressures and time ofY treatment of cresylic pitchduring hydrogenation may vary and are preferably kept within certaindesirable ranges. The. temperatures which have been useful are fromabout 300 to about 500 C. and preferably in the range of about 350 to450 C. At 350 C. a relatively long reaction time is required to producea desired degree of liquefaction while at 450 C. the time isconsiderably shor- Vamounts of tar acids.

tened. Temperatures over 450 C. may be employed, but such temperaturesare less desirable for tar acid production than those of 450 C. andlower.

The pressure of hydrogen or hydrogenating gases duringv hydrogenationmay be 500 lbs.per square inch or higher. The extent of liqueface tionis increased at higher pressures, other variables remaining constant.300 lbs. per square inch may be used, Vor higher pressures up to 3000lbs. per square inch or upV to the limit obtainable in the apparatus'inwhich the conversion is effected.

With increase of reaction timein batch processes there is an appreciableincrease in yield. From about one half hour to about 3 hours aredesirable for effecting a lioluefaction` of over 50% or of about 50% to55% of the pitch.

The hydrogenation of the cresylic pitch, as indicated above, may beconducted either in the presence of or in the'absence of a catalyst. Incertain instances the Walls of the'hydrogenation chamber have somecatalytick eifect. The small proportion vof iron oxide generally presentinthe pitch may also be catalyti'callyV active. Improved resultsareobtained when the hydrogenation is conducted in the presence of an addedcatalytic substance. Various types of' catalytic substances areapplicable such as certain metallic elements including iron,. nickel',et'c., and particularly moiybdenum sulphide, stannous sulphide, othermetallic sulphides, such as those of iron,-cobalt, nickel,A zinc,silver, mercury, lead, copper and tungsten. These `sulphid'es maybe usedalone or with additions of halids such as iodine, or halogen compoundssuch as iodoform, ethylene chloride, bromof'orm, and the. like.Molybdenum oxides, tungsten oxides,.and others with or without theaddition of elemental sulphur or of a compound containing sulphur mayalso beused. Any of the Vwe11 known sulfactive catalysts andparticularly those ofthe typewhich resist poisoning by sulphur arehighly effective in the present hydrogenation process.`

In the accompanying drawings, flow diagrams are presented whichillustrate severalexamples of methods for beneficiating `cresylic pitch.As illustrated inFigure 1 cresylic pitch is hydrogenated in a closedvessel, such as an autoclave at elevated temperatures and. pressures andfor a period as indicated above. After the desired liquefaction hasVtaken place the hydrogenated cresylic pitch is subjected to distillationto removertar acids and other compounds. The residue which remains afterremoval ,of the tar acids and other compounds generated duringhydrogenationare further hydrogenated under conditions indicated aboveto yield additional 'Ihe tar acids are separated from the hydrogenatedresidue by distillation and residues from the` distillation of thissecondary hydrogenation product can be further treated if desired.

Owing to the lfact that vthe residues from the distillation of the"secondary hydrogenation products can be further hydrogenated, acontinuous process is feasible. Such ka'prccess is illustrated in Figure2. Cresylic pitch is hydrogenated in an autoclave which may berepresented by a rectangle I. The hydrogenated cresylic pitch isdistilled in a still represented by a rectangle 2 to remove tar acids,hydrocarbons, etc. The residue from the distillation is mixed with freshcresylic pitch and the mixture is introduced into Pressures as low as`the autoclave l to be hydrogenated. A cyclic process is thus carried onand the complete utilization of the cresylic pitch is made possible.

In Figure 3, a flow diagram is shown to illus- 5 trate the pretreatmentof cresylic pitch before hydrogenation. By such pretreatment a certainamountof tar acids is formed which are separated from the pretreatedcresylic pitch. The remaining portion of the pretreated pitch is thenhydrogenated to form further amounts of tar acids and other compounds.

During hydrogenation, vent gases from the autoclave may be passedthrough dilute sulphuric aciclv for the purpose of removing ammonia thatmay be present. The gases may also be condensed or they may be washedwith oil to remove lighter hydrocarbons that form. Such lighterhydrocarbons' have a boiling range of 4 to about 20 C.

The following examples are given by way of illustration and are not tobe considered asl limitations. f

Example 1v1-A charge oi' cresylic pitch in the absence of a catalyst isplacedin` an autoclave under an initial. pressure of about 900 lbs. per

square inch and` heatedA toabout 450 C. in the presence ofAahydro'genat'ing gas. The temperature is held at this point for about.one hour.

The apparatus is thereafter cooled'. to room temperature, the pressurefalling to about 4'00 lbs.

per square inch. The liquid product formed is removedfrom the autoclaveanddistilled.. The distillate comprises about 3.2% water, 8.55% ofmaterialsl boiling to 180 (712,441470A distillate boiling from about 180C. at" atmospheric pressure to about 150- C. at 2 mm. pressur`e and aresidue of about 35.9% pitch. The above 44.4% fraction contains about84% tar acid. Thisfraction is treated to remove tar acids therefrom.

Example 2.-A charge of cresylic pitch is mixed' with about 1% by weightofmolybdenum sulphide as catalyst. The mixture in an autoclave issubmittedto an initial pressureof 900 lbs.'per' square in'ch and heatedvto 450 C. in the presence of a hydrogenating gas. The temperature isheld at' this point for about one hour. The apparatus is cooled to roomtemperature and the pressure is gradually reduced.. The hydrogenationproduct isdistilled. The distillate comprises about 3.21% water, 8.5% ofmaterial boiling to 180 C., about 55.3% distillate boiling from 180 atatmospheric pressure to 150 at 2 mm. pressure, and a residue of about'29.7% pitch. The 55.3% fraction is treated to obtain tar acids. Thisfraction contains about 82% tar acids.

Example 3.-Cresyli'c pitch is placed in an autoclave and submitted toaninitial partial hydrogenating pressure of ab'out- 1400 lbs. per squareinch and av temperature upto about'450" C. The

autoclave Vis cooled and the liquefied product is treatedV to' obtainfree tar acids. Onv distillation there are obtained aboutl 3.6% water,8% material up to. 180 C., 5.218% distillate' fronrl80 at atmosphericpressure to 150 at 2 min. pressure containing about 82% tar acids, and aresidue of about 28.4% pitch.

Example 4.-Cresylic pitch mixed with about 1% molybdenum sulphide ishydrogenated for about one-half hour at` 450 C., the.` initialhydrogenating pressureqbeing. 4about 1950 lbs. per square inch. Thebeneciated pitch comprises about. 3.7% water, 9%. material boiling up toaboutv180A C.,49.6%. distillate from' 180? at. atmospheric pressure to150 ati 2 mm; pressure taining the greater proportion of tar acids ondiscontaining about 79% tar acids, and a `residue of 31.3%. i

Example 5.-Cresylic pitch is hydrogenated .for about one hour at 400 C.in the presence of 1% molybdenum sulphide underfpressure, the initialpartial hydrogenating pressure being about 1950 lbs. per square inch.`The hydrogenated product contains about `2.8% water, 4.5% materialboiling to 180 C., 37% distillate from 180 at atmospheric pressure to150 at 2 mm. pressure containing 85% tar acids, and 43.7% pitch residue.1 Y

Example 6.--A charge of cresylic pitch is h f- `drogenated at 350-C`.for 51/2 hours in the presence of 1% molybdenum, sulphide, the initialpressure being about 1700 lbs. per sduare inch. The reaction productcontains 2% water, 5.1% material boiling up to 180 C., 24% distillatefrom 180 at atmospheric pressure to 150 at 2 mm. pressure containingabout 79% `tar acids, and 67.1% pitch residue.

Example 7.-Cresylic pitch in the presence of about 5% nickel catalyst ishydrogenated at about 275 C. for about 2 hours, the initial pressurebeing 1200 lbs. per square inch. The hydrogenated material is distilledto obtain a tar acid fraction. The yield of tar acids is about 32.1%.

Example 8.--Ptch residues obtained from a number o hydrogenated cresylicpitch batches after distillation of tar acids, are combined andhydrogenated'for 51/2 hours at 450 C. in the presence of 1% molybdenumsulphide, the initial pressure being 1700 lbs. per square inch. Theproduct comprises 3.8% water, 12.8% material boiling up to 180 C., 45.4%distillate from 180 at atmospheric pressure to 150 C. at 2 mm. pressurecontaining 41% tar acids, and 28.8% pitch residue. This residue isrehydrogenated under similar conditions. prises 25% Water, 4.95%materials boiling up to 180 C., 37% distillate from 180 at atmosphericpressure to 150 C. at 2 mm. pressure containing 20% tar acids, and 48.8%pitch residue. The latter residue may be further hydrogenated.

In the last example the pitch residue instead of being separatelyhydrogenated is alternatively mixed with fresh cresylic pitch and theresultant mixture is hydrogenated. Each residue obtained thereafter isremixed with fresh batches of cresylic pitch to be hydrogenated.

Example 9.-Raw cresylic pitch is thoroughly mixed with an excess ofabout dilute mineral acid (sulphuric acid or hydrochloric acid). Theexcess is beyond the amount necessary to neutralize alkalinity of thecresylic pitch. The resulting mixture is washed with warm water toremove soluble inorganic salts and excess acid. The washed pitch issubjected to vacuum distillation to remove water. It is subjected tofurther distillation to obtain a tar acid fraction which yields about26% tar acids.A The pitch residue remaining in the still is subjected tohydrogenation in the presence of a catalyst at about 450 C. under apartial hydrogenating pressure of over 300 lbs. per square inch for onehour either continuously or intermittently. The' hydrogenated product isdistilled to recover volatile products including hydrocarbons, tar acidsand a residue. The distillate is .treated to separate tar acids fromneutral oil. About 50% of the hydrogenated product boils up to about 275C. at atmospheric pressure. The distillate thus obtained contains about80% tar acids.

In each of the above examples a fraction contillation of thehydrogenated pitch, is treated in the. conventional manner for obtainingfree tar acids and neutral oil. vFor example, the tar acid fraction ismixed withl sodium hydroxide to form sodium phenolates which separateout of the neuti'aloil in the form-of a layer. vThe phenolateA layer isthen subjected to a springing treatment with carbon dioxide.` Thephenols are set free and may be' fractionated? to obtain individualphenolic compounds. From a i hydrogenated cresylic pitch yielding taracids to the extent of about 50% of the total yield of liquefiedproduct, there is obtained the following:

. Per cent Phenol 1.2 Cresols 23.1 Xylenols .g c 33.1 `Tar acids boilingfrom 220 to 240 C 27.5 Tar acids boiling above240"` C 15.1

The resulting product com- Alternatively, ineach of the above examples,tar acid oil produced and'containing Vthe tar acids and neutral oilis avaluable product as such. Among other uses the tar acid oil serves, forinstance, as a material in the manufacture of certain insecticide oils.Y

By means of the process of the present invention, cresylic pitch whichhas heretofore been commercially valueless, is converted into productsthat are of considerably greater value than the pitch. The tar acids arecombined with those of the tar acid plant, thereby increasing singlering tar acid production. Neutral oil and hydrocarbons obtained in thehydrogenation process are important commodities otherwise lost and nowfinding increased diversified application.

While certain periods of time, temperatures, and pressures areprescribed in the above examples, these factors may be so adjusted toeach other that a substantial proportion of constituents in the pitch isconverted intotar acid fractions distillable without decomposition.

It is apparent from the above description that various changes may bemade in the procedures without departing from the spirit and scope ofthe invention or sacrificing all of its material advantages, theprocedures hereinbefore cited by way of illustration being merely thepreferred embodiments thereof.

What is claimed is:

1. In a process of producing free tar-acids from cresylic pitch residuethat is non-distillable Without excessive decomposition and coking, andthat is formed by distillation of a distilland substantially completelyconsisting of chemically separated free tar-acids, which tar-acids areobtainable by reacting tar-acids in tar-acid-bearing oil with causticalkali to form tar-acid salts, removing so-formed tar-acid salts fromunreacted oil, and freeing the tar-acids from said salts in a springingoperation; subjecting the said cresylic pitch residue to a pressure ofover 300 pounds per square inch at a temperature in substantially therange of 300 C. to 500 C. in contact with hydrogen to eiect liquefactionof material in the said cresylic pitch residue and thereby to obtaintaracid material from which free tar-acids are distillable withoutdecomposition, and separating free tar-acids comprising phenol, cresolsand xylenols from the resulting mass.

2. In a process of producing free tar-acids from cresylic pitch residuethat is non-distillable without excessive decomposition and coking, andthat is formed by distillation of a distilland substanlagsaegaemtiallyfv completely'gconsistings offY chemicallyL separated;- freetari-acids;` which tar-acids are; obtainable by: reactingtan-acidsamtar-acdi-bearing; oil

with caustic alkaliitiol form tan-acidsalts; remowing so-formedvtar-acid salts from unreaeted; oil, and freeing: the' tari-acids from4said. salts? in.A a springing operation; subjectingthesaid cresy-licpitch residue` to4 av pressure of; from substantially 20 atmospheres;tou 200 atmospheres: at: a; tempera@- turev in substantially: therangetof'f`300f 0;. to 500 C; in the presence: off a catalyst'. andlin-v contact with hydrogen tot effect: liquefacti'on. of: material inthev said cresylic pitch residue and thereby to obtain tar-acidmaterial: from which: freev taracidsI are distillable withoutdecomposition, and distilling free tar-acids comprising phenol,.cresolsand xylenols from the resulting massL 3'. In a process of` producing.freeitar-acids from cresylicpitch residue that isfnondisti1lablewithout' excessive decompcsitionzandY coking,xand that 20 is formed bydistillation of a distilland substantially completely consisting ofchemically sepa.- rated free. tar-acids, which tar-acids. are obtainableby reacting tar-acids in' tar-acid-bearing oil with caustic alkali toform tar-acid salts', removing so-formed tar-acid saltsifrom unreactedoil, and'freeing thei tar-acids from said salts in a springingoperation; contacting the said cresylic pitchi residuev and dilute,lmineral acid to acidify theY mass, Washing the acidied mass to removefree` mineral acid therefrom', distilling the sotreated cresylic pitchresidue to obtain a fraction containing free tar-acids, subjecting theresulting undistilled residual portion o f the acid-treated cresylicpitch residue to a pressure of over 300 pounds. per square inch at atemperature in substantially the range of 300 C. to 500 C. in contactWith hydrogen to effect liquefaction of the said undistilled residualportion of the` said acidtreated cresylic pitch residue and thereby toobtain' tar-acid material from which free tar-acids are distillable;Without decomposition, and distilling free tar-acids comprising phenol,cresols and xylenols from the resulting said tar-acid material.

CHARLES F. WINANS.

